Use empty_like in scatter

cpp/include/cudf/lists/detail/copying.hpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020, NVIDIA CORPORATION.
+ * Copyright (c) 2020-2021, NVIDIA CORPORATION.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -48,21 +48,6 @@ std::unique_ptr<cudf::column> copy_slice(lists_column_view const& lists,
                                          rmm::cuda_stream_view stream,
                                          rmm::mr::device_memory_resource* mr);
 
-/**
- * @brief Create a single-level empty lists column.
- *
- * An empty lists column contains empty children so the column's
- * basic type is recorded.
- *
- * @param child_type The type used for the child column.
- * @param stream CUDA stream used for device memory operations and kernel launches
- * @param mr Device memory resource used to allocate the returned column's device memory.
- * @return New empty lists column.
- */
-std::unique_ptr<cudf::column> make_empty_lists_column(data_type child_type,
-                                                      rmm::cuda_stream_view stream,
-                                                      rmm::mr::device_memory_resource* mr);
-
 }  // namespace detail
 }  // namespace lists
 }  // namespace cudf

cpp/include/cudf/lists/detail/scatter.cuh

@@ -526,10 +526,7 @@ struct list_child_constructor {
 
     if (num_child_rows == 0) {
       // make an empty lists column using the input child type
-      return make_empty_lists_column(
-        source_lists_column_view.child().child(lists_column_view::child_column_index).type(),
-        stream,
-        mr);
+      return empty_like(source_lists_column_view.child());
     }
 
     auto child_list_views = rmm::device_uvector<unbound_list_view>(num_child_rows, stream, mr);

cpp/src/lists/copying/copying.cu

@@ -84,19 +84,6 @@ std::unique_ptr<cudf::column> copy_slice(lists_column_view const& lists,
                            std::move(null_mask));
 }
 
-std::unique_ptr<cudf::column> make_empty_lists_column(data_type child_type,
-                                                      rmm::cuda_stream_view stream,
-                                                      rmm::mr::device_memory_resource* mr)
-{
-  return cudf::make_lists_column(0,
-                                 make_empty_column(data_type{type_to_id<offset_type>()}),
-                                 make_empty_column(child_type),
-                                 0,                                  // Null count
-                                 rmm::device_buffer{0, stream, mr},  // Null mask
-                                 stream,
-                                 mr);
-}
-
 }  // namespace detail
 }  // namespace lists
 }  // namespace cudf

cpp/tests/partitioning/partition_test.cpp

@@ -310,3 +310,23 @@ TEST_F(PartitionTestNotTyped, ListOfListOfIntEmpty)
   CUDF_TEST_EXPECT_TABLES_EQUAL(table_to_partition, result.first->view());
   EXPECT_EQ(3, result.second.size());
 }
+
+TEST_F(PartitionTestNotTyped, ListOfListOfListOfIntEmpty)
+{
+  cudf::test::lists_column_wrapper<int32_t> level_3_list{};
+
+  fixed_width_column_wrapper<int32_t> level_2_offsets{};
+  std::unique_ptr<cudf::column> level_2_list =
+    cudf::make_lists_column(0, level_2_offsets.release(), level_3_list.release(), 0, {});
+
+  fixed_width_column_wrapper<int32_t> level_1_offsets{0, 0};
+  std::unique_ptr<cudf::column> level_1_list =
+    cudf::make_lists_column(1, level_1_offsets.release(), std::move(level_2_list), 0, {});
+
+  auto table_to_partition = cudf::table_view{{*level_1_list}};
+  fixed_width_column_wrapper<int32_t> map{0};
+
+  auto result = cudf::partition(table_to_partition, map, 2);
+  CUDF_TEST_EXPECT_TABLES_EQUAL(table_to_partition, result.first->view());
+  EXPECT_EQ(3, result.second.size());
+}